Anthocyanins are an important and widespread group of coloring agents found in nature. Anthocyanins are water-soluble color pigments found primarily in higher plant flowers, fruits and vegetables. The anthocyanin used to produce the natural colorant of the present invention is derived from the cell line Daucus carota. The cell line of Daucus carota produces an excess of a single anthocyanin which is a secondary metabolite. The anthocyanin derived from the cell line of Daucus carota is an intensely colored, water-soluble pigment whose coloration varies from dark reds to purples and blues depending on pH level.
U.S. Pat. No. 4,172,902 discloses that it is known that most naturally occurring anthocyanins are intensely colored at pH levels below 3 but that anthocyanins are virtually colorless in an environment having pH values above 3. This patent also discloses the anthocyanin, peonidin 3-(dicaffeylsophoroside)-5-glucoside derived from "Heavenly Blue" Morning Glory, which according to the patent is useful for producing stable colors in food and beverages at pH values from about 2.0 to about 8.0.
Additionally, it is generally known that Daucus carota cells can be grown in cell suspension cultures in a defined liquid media as well as in callus cultures grown on plates containing the same defined liquid media as used in the suspension cultures with the addition of 1.0% agar. Generally, however, isolation of natural colors from plant flowers, fruits or vegetables requires the use of the whole plant rather than cells grown in a tissue culture. As a result of using a whole plant, the growth of the plant is slower, less manipulatable and is restricted due to natural geographic limitations, such as climate, soil, water, pests, seasonal growth, transportation, etc.
A naturally produced coloring agent is of considerable importance and commercial interest due to the present need to replace the currently used artificial coal tar (azo type) dyes as additives in food products. The artificial coal tar dyes are presently believed to be carcinogenic agents. Anthocyanins have several advantages as a naturally produced coloring agent in that anthocyanins have been present in human and animal food chains for generations without apparent adverse effects on health. Further, anthocyanins produce brightly colored red hues and are water-soluble. However, anthocyanins generally are not stable over a wide pH range which is necessary in order for a natural colorant to be useful as a coloring agent in food products.